generally safety pins are used to baste a quilt sandwich---not straight pins- that seems really (hazardous)
thread basting is an option- many of us prefer thread basting over dealing with all the pins.
often people leave out the batting when using minkie- it is very warm & heavy on it's own.
lengthen your stitch length, loosen your tension, put together a small *practice* sandwich to practice on if you have any extra minkie, fabric,batting...and practice a bit adjusting as needed until you get your stitches looking like you want them to look. all those straight pins may be causing some of the problems-
you might want to try basting spray. or do a search on thread basting...it is alot faster than all those pins, holds better & doesn't poke you constantly
try to set a card table or something up beside you to help hold the weight...practice before working on the *real quilt*. it is a beautiful quilt!
good luck.